1. Field of the Invention
The present invention relates to electronic packaging, and more particularly, to a cavity and bump interconnection structure for use in electronic packaging.
2. Description of Related Art
The interconnection of the electronic components, especially high density electronic components and printed wiring boards, presents recurring problems for which many conventional solutions exist. Prior art interconnections techniques that have been used to interconnect two printed wiring boards or a flexprint and a printed wiring board include soldering connectors to both subassemblies and then subsequently mating the connectors. The use of connectors results in bulky, heavy, relatively expensive, and in many cases, an impractical solution. For example, conventional micro-connectors, because of their small size, require soldering or other expensive wiring techniques. Most micro-connectors cannot handle a 3 mil to 5 mil (0.0762 mm to 0.1270 mm) or smaller line width and spacing in an efficient manner.
Many conventional interconnection systems utilize pads or electrically conductive dots, such as the well-known gold-dot interconnection structure, as a means of providing the interconnection, such as is disclosed in U.S. Pat. Nos. 4,125,310 and 4,453,795. These patents describe a plurality of generally resilient metallic raised projections. In the latter patent, a resilient backup mechanism is used to avoid overstressing and squashing of the resilient projections or contacts beyond their elastic limit, which overstressing precludes repeated mating and unmating of connectors incorporating such projections. While these terminations otherwise effectively and reliably interconnect mating circuits, their manufacture can be difficult, time consuming and costly. Furthermore, the manufacturing process for forming such bumps is limited to a size of about 2 mil (0.0508 mm) in diameter. These bumps also require proper support, without exposing them to delamination due to outgassing from support materials during or after production or to inattention to thermal matching with its surrounding materials, or to possible electrical or chemical interaction with the surrounding materials.
Another interconnection technique is described in copending U.S. patent application Ser. No. 07/989,612, filed Dec. 14, 1992, now U.S. Pat. No. 5,288,235 assigned to the assignee of the present invention. This invention comprises an electrical connector for a flat cable or circuit having contacts or interconnects formed as a bulge arrangement or configuration. The bulge-type contacts or interconnects are shaped to provide a pointed, serial or continuous bulge configuration, such as one or more upsets, wrinkles, folds and creases, e.g., V-shaped and hollow shaped, both in one or more of conductors in the circuit and in any insulation underlying the conductors. The shape of the bulge configuration is maintained by a support, which also is selected to physically and chemically match with materials surrounding it.
The bulge configurations result from forming the cable to provide one or more bulges in the circuit having concave and convex portions configured as single upsets, or a series of single upsets, or a linear bulge having a V-shaped appearance, or a linear bulge. The support is shaped in accordance with the bulge into which it fits. Thus, it may comprise a dielectric resin for fitting into the pointed upsets or an extending bar with a V-shaped part, which respectively fits into the bulge concave portions or portion. A backing may be applied to the underside of the cable under the single upset, or the bar itself may be affixed to the underside of the circuit by an adhesive or secured into a mating bar on the upper side of the circuit.
The bulge configuration may comprise a series of upsets or a linear or curved wrinkle, fold or crease extending in a pattern across at least some of the conductors and the underlying dielectric circuit material on only one side of the conductors is exposed, although the conductor may be exposed on both sides to enable, for example, a plurality of the circuits to be stacked together and their bulges to interfit and electrically interconnect with adjacent bulges. The pattern may extend across the width of the circuit in any desired fashion, such as at fight angles, diagonally, undulating, in the form of a "V", curve, or an arc.
The present invention is intended to provide an additional interconnection technique that is particularly well-adapted for interconnecting two printed wiring boards or a flexprint circuit and a printed wiring board. Therefore, it is an objective of the present invention to provide an improved cavity and bump interconnection structure for use in electronic packaging. It is a further objective of the present invention to provide an interconnection structure that provides for the interconnection of two printed wiring boards or a flexprint circuit and a printed wiring board.